Feed is what you feed the calf. A ration is usually a specially formulated mix of feedstuffs designed for a specific feeding goal. There are hundreds of different rations - they vary with regional feed types, animal needs, etc. Heifers and younger steers are often fed a growing or developing ration that has the nutrients needed to maximize her growth potential. Those rations aren't always formulated to allow for enough finish/fat/cover. That's when you switch over to a finishing ration. That is just what it says.. it finishes the animal - provides the nutrients to for them to put on enough fat, muscle, & cover to be considered a finished ready for market animal. There is far more to it than that...